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The setup is the same as an AOV except we use a light path expression instead of an AOV channel name. We can also use a short descriptive name (e.g. lpe:diffuse) as well as the long LPE expression (e.g. lpe:CD<L.>CD[<L.>O]).

Additionally, we can group the outputs by light groups and/or by geometry set up by a lpegroup.

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For DisplayChannel, we can use either the short name or long expression, e.g., lpe:diffuse or lpe:CD<L.>CD[<L.>O]

Code Block
DisplayChannel "color lpe:diffuse"

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Code Block
DisplayChannel "color lpe:CD<L.>CD[<L.>O]"

Basic LPEs

For basic workflows, the following LPE are recommended. Note that we are specifying the DisplayChannel and a name (which can be most anything). Note that these LPE will collect the light interaction from different lobes of materials and store them in the same AOV. For example: reflections from the Glass Lobe in PxrSurface will be combined with other specular reflections in the direct and indirectSpecular AOVs. This can simplify the outputs.

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Note
Note that the first eight of these expressions are both disjoint and exhaustive; any individual light path will match exactly one of them. As a result, rendering out all eight of them and then compositing them together will produce the equivalent of the beauty image.

 

Caustics are not included in the built-in list because they overlap with lpe:indirectdiffuse. with indirectdiffuse lpe:C<RD>[DS]+[<L.>O] However, you can select caustics with the expression lpe:CD[S]+[<L.>>O]

Custom LPE

RenderMan for Maya

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